Power on problems

I have a computer (with ATX case) that worked fine a couple of years. Suddenly, I cannot start the computer from the power button (nothing changed meantime, not even the location of it). The only solution for strating the computer is to unplug the power supply cord from the socket, stay five seconds and plug in it again and the computer starts (without pressing the power button) immediatly.
I've tried to manage this changing the BIOS settings but nothing happened (only the achievment of don't starting at all ... neither with above procedure...
There is somebody having a solution for this issue? I know it works but it is a upsetting job to work with power cord every time when you want to start the computer.

Well, the first thing I would suggest is to check the switch itself....could be faulty. Other than that, possibly plugging it into a switched outlet/power strip and use that as your switch....but replacing it would be in your best interest.

In my experience (limited), when I unplugged computers than the PSU disipated all the electricity it contained. Of course, I don't have much experience. You could try holding the Power button down for a while (sometimes a mechanical power button needs this). It seems like an unusual problem...

sounds like the switch to me. The hold current isn't being properly drained(or isn't holding) and is causing it to think the switch hasn't been switched from off to on. Its a fairly common problem, not only in computers but in anything that uses that type of switching mechanism.